Benchmark: Map vs Object with Number Keys

Script Preparation code:

var object = Object.fromEntries(new Array(100000).fill(1).map((_, i) => [Math.random() * 100000 | 0, 'value']));
var map = new Map(Object.entries(object));

Tests:

Iterate Object
let lastValue = ''; for (var key in object) lastValue = object[key];
Iterate Map
let lastValue = ''; for (var [key, value] of map) lastValue = value;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Iterate Object
Iterate Map

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Test name	Executions per second
Iterate Object	416.0 Ops/sec
Iterate Map	4357.1 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the provided benchmark test case.

**Benchmark Definition and Preparation Code**

The benchmark measures the performance difference between using an `Object` and a `Map` data structure in JavaScript, specifically with numeric keys. The preparation code creates two objects: `object` and `map`. `object` is created using the `Object.fromEntries` method, which converts an array of key-value pairs into an object. On the other hand, `map` is created directly from the `object` using the `Map` constructor.

The script preparation code looks like this:
```javascript
var object = Object.fromEntries(new Array(100000).fill(1).map((_, i) => [Math.random() * 100000 | 0, 'value']));
var map = new Map(Object.entries(object));
```
**Comparison of Options**

In this benchmark, we have two main options being compared:

1. **Object**: Using an `Object` data structure with numeric keys.
2. **Map**: Using a `Map` data structure with numeric keys.

**Pros and Cons of Each Approach**

**Object:**

Pros:

* Faster creation time for large objects
* Easier to implement certain algorithms (e.g., property iteration)
* Familiar interface for many developers

Cons:

* Slower iteration performance compared to Map, especially for large datasets
* May lead to slower performance due to the object's inherent properties (e.g., string keys may be optimized differently)

**Map:**

Pros:

* Faster iteration performance, especially for large datasets
* Optimized for iteration and key access
* More intuitive interface for algorithms that rely on iterator-like behavior

Cons:

* Creation time can be slower compared to Object
* May require additional syntax or library support for certain use cases (e.g., custom iteration)

**Library Considerations**

In this benchmark, we don't see any external libraries being used. However, in general, when working with large datasets or performance-critical code, you might consider using optimized libraries like Lodash's `_.mapValues` or a custom iterator implementation to further improve performance.

**Special JavaScript Features or Syntax**

The script preparation code doesn't include any special JavaScript features or syntax that would affect the benchmarking results. The focus is on comparing the performance of Object and Map data structures in JavaScript.

**Alternatives**

If you want to explore alternative approaches, here are a few options:

1. **Set**: Using a `Set` data structure instead of `Map`. Sets are optimized for fast lookup and insertion operations.
2. **Array**: Using an array with numeric indices instead of `Object` or `Map`. Arrays offer faster iteration performance but may not be suitable for large datasets or key-value pairs.
3. **Custom Iterator**: Implementing a custom iterator using a loop or recursion to iterate over the data structure. This approach can provide more control over the iteration process.

Keep in mind that these alternatives might affect the overall performance and readability of your code, so consider your specific use case and requirements before choosing an alternative approach.

Related benchmarks:

Map vs Object with Number Keys (version: 0)

Comparing performance of: Iterate Object vs Iterate Map

Created: 2 years ago by: Guest

Jump to the latest result

Iterate Object

Iterate Map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):